Many sources pinpoint the unchangeable features of some Spartan institutions as a key aspect of Spartan εὐνομία.
Aristotle wrote extensively on Spartan institutions as well as praised Lycurgus as a great lawgiver who established the laws of Sparta.
Even Thucydides stressed that the Dorians established excellent laws and Sparta employed the same constitution for more than four hundred years. (… τετρακόσια καὶ ὀλίγῳ πλείω ἐς τὴν τελευτὴν τοῦδε τοῦ πολέμου ἀφ᾽ οὗ Λακεδαιμόνιοι τῇ αὐτῇ πολιτείᾳ χρῶνται).